Crystal structure of 13-(E)-(2-amino-benzyl-idene)parthenolide

Abstract

The title compound, C₂₁H₂₅NO₃ [systematic name: (1aR,4E,7aS,8E,10aS,10bR)-8-(2-amino-benzyl-idene)-1a,5-dimethyl-2,3,6,7,7a,8,10a,10b-octa-hydro-oxireno[2',3':9,10]cyclo-deca-[1,2-b]furan-9(1aH)-one], was synthesized by the reaction of parthenolide [systematic name (1aR,7aS,10aS,10bS,E)-1a,5-dimethyl-8-methyl-ene-2,3,6,7,7a,8,10a,10b-octa-hydro-oxireno[2',3':9,10]cyclo-deca-[1,2-b]furan-9(1aH)-one] with 2-iodo-aniline via Heck reaction conditions. The mol-ecule is composed of fused ten-, five- (lactone), and three-membered (epoxide) rings. The lactone ring shows a flattened envelope-type conformation (r.m.s. deviation from planarity = 0.0477 Å), and bears a 2-amino-benzyl-idene substituent that is disordered over two conformations [occupancy factors 0.901 (4) and 0.099 (4)]. The ten-membered ring has an approximate chair-chair conformation. The dihedral angle between the 2-amino-benzyl-idine moiety (major component) and the lactone ring (mean plane) is 59.93 (7)°. There are no conventional hydrogen bonds, but there are a number of weaker C-H⋯O-type inter-actions.

Keywords: 2-iodo­aniline; Heck product; crystal structure; parthenolide.

Figure 1

The mol­ecular structure of the title compound with ellipsoids drawn at the 50% probability level.

Figure 2

A packing plot showing the stacking of 2₁ screw-related adjacent lactone groups. The stacking direction, shown by a dashed line, is parallel to the crystallographic b axis. For emphasis, lactone-group atoms are depicted as solid balls. For clarity, hydrogen atoms and minor disorder components are omitted.